In inkjet recording, recording is accomplished by ejecting small ink droplets by various mechanisms to form dots by adhesion on a recording paper. Unlike the dot impact recording method, there is no noise, it is easy to form a full-color image and printing can be performed at high speed.
However, the inks used for inkjet recording were aqueous inks using ordinary direct dyes or acidic dyes which did not easily dry out. Thus the properties required of the inkjet recording paper used for this inkjet recording method were that it allowed high-speed drying of the ink, that it gave a high printing density, and that there was no bleeding or smudging of ink, nor lenticulation of the recording paper due to ink absorption. Methods of manufacturing a high-quality inkjet recording paper satisfying these requirements by cast coating have already been proposed (Japanese Patent Application Public Disclosure Sho 62-95285, 63-264391, Japanese Patent Application Public Disclosure Hei 2-274587 and 5-59694 (all Koho)). In all these methods, a cast coating paper with high gloss is obtained by simultaneously transferring a recording layer comprising a pigment having a synthetic silica as its main component and a binder under pressure to a heated mirror surface in a wet state before it has dried so as to transfer a mirror finish, and drying. However, the gloss of the outermost layer thus formed was low, and a glossiness of the same quality as that of a silver halide photographic paper could not be obtained.
On the other hand, an inkjet recording paper of similar quality to that for silver halide photography, comprising a recording layer having a hydrophilic binder such as polyvinyl alcohol or gelatine and inorganic fine particles on a resin-coated paper (“RC paper”), comprising a coating layer of polyolefin with a white pigment on at least one surface of a base paper, has been proposed (Japanese Patent Application Public Disclosure Hei 10-119423 (Koho), Japanese Patent Application Public Disclosure Hei 11-20306 (Koho)). However, in the case of these inkjet recording papers, a resin-coated paper which is not air-permeable is used as a support, so some time was required for drying after coating the recording layer, and productivity was extremely low.
The Inventors, as a result of intensive studies of the above disadvantages, found that an extremely good inkjet recording medium of similar quality to that of silver halide photographic papers could be obtained by applying a recording layer comprising polyvinyl alcohol, treating the recording layer surface with a mixed solution of borate/borate acid while it was still in the wet state, and bringing it into pressure contact with the heated mirror surface while the recording layer was still in the wet state. Particularly good results were obtained by using two types of polyvinyl alcohol having different average saponification degrees. They thereby arrived at the present invention.
It is therefore an object of this invention to provide a glossy inkjet recording medium of the same quality to that of silver halide photographic papers having good inkjet recording properties and excellent productivity.